The present invention relates generally to a template for the surgical implantation of needles into a patient""s body, and more specifically to a template for implantation of needles for prostate brachytherapy.
Various forms of cancer are treated by exposing cancerous tissues to controlled doses of radiation. One technique for delivering a dose of radiation to cancerous tissue is brachytherapy. Brachytherapy is a procedure that involves the implantation of radioactive sources in or near cancerous tissue in order to apply a desired dose of radiation. By implanting a radioactive source in or near targeted cancerous tissue, the desired radiation dose can be delivered, while limiting radiation exposure to other tissues. Brachytherapy which utilizes needles containing one or more radioactive sources to deliver the desired radiation dose into a patient is known to be an effective technique for treating prostate cancer.
In administering brachytherapy, a doctor will formulate a three dimensional dosimetry pattern for the placement of radioactive sources within a cancerous organ. In the seed implantation form of brachytherapy, radioactive xe2x80x9cseedsxe2x80x9d are discharged within the targeted cancerous organ via one or more hollow needles in accordance with the predetermined dosimetry pattern and these seeds are left inside the patient to deliver the desired radiation dosage. The implanted seeds are left within the patient to continue to deliver radiation even after the patient leaves the hospital. The level of radioactivity of the implanted seeds then gradually deteriorates until it becomes insignificant.
Another brachytherapy technique is to insert into and remove from a patient more intense radioactive sources in a timed pattern via hollow needles inserted into a target region. This technique, known as high dose rate brachytherapy (xe2x80x9cHDRxe2x80x9d) delivers a desired dosage in a short amount of time, but avoids permanently implanting radioactive seeds. During an HDR treatment a timed pattern of intense radioactive sources are inserted and retracted through the needles over several minutes. This technique requires that the brachytherapy needles remain in the patient for many hours while a series of HDR treatments are administered.
For brachytherapy to have its desired effect it is important that a doctor be capable of precisely placing the brachytherapy needles into the patient. Needles are placed using a template which includes a grid of needle holes. Each needle hole on the grid may be uniquely identified by its own vertical and horizontal coordinates. It is intended that such a needle template be maintained at a constant position with respect to the patient""s body surface and the cancerous organ. Thereby the preplanned dosimetry pattern may be implemented by inserting the needles through their designated coordinates on the template and into the patient.
In conjunction with a needle template, an ultrasound device is used to monitor the placement of the needles. In the case of prostate brachytherapy treatment, the ultrasound device is inserted into the rectum of the patient. During treatment, the needle template may be directly mounted on the ultrasound device to maintain a constant relative position between them. The needle template can also be sutured in place on the patient""s body.
Once the needles have been inserted into the patient, it is desirable to provide a locking mechanism in the template to hold the needles in place so that the needle insertion depth will not change unintentionally. A conventional design for a locking mechanism is to make the template from a xe2x80x9csandwichxe2x80x9d of three plates through which the needle holes extend. In this design, the outer and inner plates are fixedly positioned with respect to one an other and the middle plate moves slidably in a vertical direction between the two outer plates. Once the needles have been inserted through the template as desired, the needles are locked by turning a screw to apply vertical force to the middle plate thereby causing the middle plate to apply a vertical force to the needles in the template, preventing their unintentional movement.
For prostate brachytherapy, needles are inserted through the perineum of a patient to deliver a radioactive source to a cancerous prostate gland. To perform this procedure the patient is placed in thelithotomy position. The needle template is supported in a vertical upright position so that the needles may be inserted into the patient on a flat horizontal plane.
In attempting to maintain a constant position of the template relative to the patient during prostate brachytherapy, the template is sutured to the patient""s skin in the perineum region. To support the template in place relative to the perineum, and to allow the sutures to be made, the template is rested in close contact with the surface of the perineum.
However, it is difficult to secure the known templates in place as these are generally square or rectangular and flat on the front and back surfaces. Flat templates are inconsistent with the shapes of patients"" perineums.
In an attempt to address this problem, the gaps between the skin of the patient and the template have been stuffed with material such as gauze. However, such gauze stuffing is often irregular and can result in a cleanliness problem as the stuffing absorbs blood. Also, gauze stuffing may interfere with making a good suture of the template to the patient.
The present invention is directed to a brachytherapy needle template comprising an inclined and/or curved support backing conforming to a shape of a part of the patient""s body. This support backing includes suturing eyelets which, when the device is in an operative position, are located adjacent to the patient""s skin. This inclined and/or curved support backing allows the needle grid portion of the template to remain vertical when placed against the patient so that the needles may be inserted horizontally.
The present invention is further directed to a needle lock mechanism for holding the needles in place once they have been inserted into a patient. The needle lock mechanism comprises an arrangement of two plates, one of which moves slidably with respect to the other wherein the movable plate slides within a vertical channel formed, for example, by placing horizontal pins in a portion of the support backing. After the brachytherapy needles have been placed through the plates, a vertical force is placed on the movable plate and the force on the movable plate locks the needles in place.